What are the most common bacterias found on a homes exterior?

The most common organic growth on the exterior of a homes roof, house siding and driveways are primarily algae, moss, mildew (often called mold) and lichen. Each of these bacteria have slight variations in color and look. The way to take notice is by the colorful typically green appearance on a homes exterior. When standing from far away the bacteria appears to have a slight haze or dripping look often caused by water running down. Upon closer inspection we notice the growth has spores and is in fact a living growing organism.

Most bacteria growth comes from days in constant sunlight, water, humidity and exposure to the outside environment. Out of the four main bacteria's mildew is the only one that does not need sunlight to produce its energy and live on, instead they feed off the organic matter they are attached to. 

Meanwhile the other three bacteria's algae, moss and lichen use photosynthesis to combine sunlight and water into their own food to thrive on. Photosynthesis is a process done by plants where they use light energy, water and carbon dioxide to fuel their growth structure. As a byproduct of this process oxygen is made.

At a quick glance it may be difficult to say which is which, but when we look at what features are present we can better tell what bacteria we have at hand.

​Generally lichens look like this

Moss generally look like this

The differnanciation from mildew and algae is their feel when touched. Lichen and moss feel prickly and like an actual plant forming. The mildew and algae do not have this outward appearance, their look is thin on its surface. Moss and lichen do not have roots exactly but they do have a root like structure with lichens being much more stubborn to pull off. Moss can be determined by its fuzzy appearance and color variation of green, yellow and at times brown. Lichens come in green or light green with a almost barnicle like look.

Here are a few examples on algae and mildew

In conclusion these are the most common bacterias found on a homes exterior.
For tips on cleaning these please refer to our website articles.

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